Correction image creation device, radiographic imaging device, imaging device, computer readable medium and correction image creation method

ABSTRACT

A correction image creation device includes: an acquisition unit that acquires at least one original image, which is a basis when creating a correction image used in offset correction with respect to an image that has been obtained by imaging; a determination unit that determines whether or not noise from the exterior is superimposed on the original image; and a cancellation unit that cancels creation of the correction image in a case in which it has been determined by the determination unit that noise from the exterior is superimposed on the original image.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of PCT International Application No.PCT/JP2012/079303 filed on Nov. 12, 2012, which claims priority under 35U.S.C. §119 (a) to Japanese Patent Application No. 2012-082557 filed onMar. 30, 2012. Each of the above applications is hereby expresslyincorporated by reference, in its entirety, into the presentapplication.

TECHNICAL FIELD

The present invention pertains to a correction image creation device, aradiographic imaging device, an imaging device, a computer readablemedium, and a correction image creation method, and particularly relatesto a correction image creation device, a radiographic imaging device, animaging device, a computer readable medium, and a correction imagecreation method that create a correction image for offset correction.

BACKGROUND ART

Conventionally, imaging devices such as television cameras areconfigured to use clamping to set the black level of the imaging resultto a predetermined signal level. For example, CCD solid-state imagesensors use sensor portions arranged in a matrix to photoelectricallyconvert incident light and sequentially transfer and output storedcharges obtained as a result. CCD solid-state image sensors areconfigured in such a way that a partial region of an imaging surfacecomprising the sensor portions arranged in a matrix in this way isshielded from light to create an optical black region, and the opticalblack level can be detected by the output signal level of this opticalblack region. Because of this, imaging devices are configured tointegrate the output signals of imaging elements obtained from theoptical black region to obtain a predetermined evaluation value andoffset the output signal levels of the imaging elements so that thisevaluation value becomes a predetermined value, thereby forming afeedback loop to set the black level of the imaging result to apredetermined signal level.

However, in these imaging devices, when the signal level of the imagingresult obtained from the optical black region momentarily changes due tonoise getting mixed in, the evaluation value temporarily changes, andthe black level needs to be corrected to correct this change.

Japanese Patent Application Laid-open (JP-A) No. 2003-110943 discloses atechnology which, in an imaging device, detects an optical black levelresulting from an output signal level of an optical black region inwhich a partial region of an imaging surface has been shielded fromlight and offsets the output signal level of an imaging element inaccordance with the detection value. Specifically, the imaging deviceintegrates, by frame, the luminance level obtained from the opticalblack region to detect an evaluation value representing the opticalblack level of the imaging result, uses this integrated value as adetection value resulting from detection data, offsets the luminancelevel of image data using a correction value based on this, and performsprocessing that clamps the black level of the imaging result to apredetermined signal level.

Furthermore, in recent years, digital imaging devices that use flatpanel radiation detectors—or what are called flat panel detectors(FPDs)—having a phosphor and a large-area amorphous silicon sensor inclose contact to directly digitalize a radiographic image withoutinvolving an optical system or the like have come into practical use.Furthermore, FPDs that use amorphous selenium, lead iodide (PbI₂), andmercury iodide (HgI₂), for example, to convert radiation into electronsand use a large-area amorphous silicon sensor to detect the electronshave similarly come into practical use. These FPDs show promise asnext-generation digital imaging devices because in principle they arecapable of capturing not only still images but also moving images.

The sensors used in FPDs comprise several million pixels, and thecharacteristics of the pixels differ from one another. Thecharacteristics particularly important for image sensors are the darkcurrent characteristic and the sensitivity characteristic. Therefore, inFPDs, offset correction for correcting these characteristics isimplemented, and the sensors are used as sensors in which thecharacteristics of the pixels are substantially uniform.

SUMMARY OF INVENTION Technical Problem

In the technology of JP-A No. 2003-110943, when acquiring the correctionvalue for offset correction, in order to obtain a correction value fromwhich noise has been removed and whose precision is high, uniquefunctions become necessary, and in order to acquire that correctionvalue, a certain amount of required time ends up being required. Inimaging devices and radiographic imaging devices, a technique for easilycreating a correction image with little noise for offset correction hasbeen desired.

The present invention provides a correction image creation device, aradiographic imaging device, an imaging device, a computer readablemedium, and a correction image creation method which, when creating acorrection image for offset correction, can easily create a correctionimage with little noise while ensuring that a correction image havingnoise superimposed thereon is not created.

Solution to Problem

A correction image creation device of the present invention includes: anacquisition unit that acquires at least one original image, which is abasis when creating a correction image used in offset correction withrespect to an image that has been obtained by imaging; a determinationunit that determines whether or not noise, from an exterior, issuperimposed on the original image; and a cancellation unit that cancelscreation of the correction image in a case in which it has beendetermined by the determination unit that noise from exterior issuperimposed on the original image.

According to this correction image creation device, at least oneoriginal image, which is a basis when creating a correction image usedin offset correction with respect to an image that has been obtained byimaging is acquired by the acquisition unit, whether or not noise fromthe exterior is superimposed on the original image is determined by thedetermination unit, and creation of the correction image is cancelled bythe cancellation unit in a case in which it has been determined by thedetermination unit that noise from the exterior is superimposed on theoriginal image.

In this way, according to this correction image creation device, bycancelling creation of the correction image in a case in which noisefrom the exterior is superimposed on the original image, a situationwhere a correction image having noise superimposed thereon is createdcan be avoided, and, as a result, a correction image with little noisefor offset correction can be easily created.

Furthermore, the correction image creation device of the presentinvention may be configured in such a way that, in a case in which ithas been determined that noise from the exterior is superimposed on theoriginal image, the cancellation unit cancels creation of the correctionimage using the original image on which the noise is superimposed.Because of this, a situation where an original image having noisesuperimposed thereon is used as an image for offset correction can beavoided.

Furthermore, the correction image creation device of the presentinvention may be configured to further include a creation unit thatcreates the correction image using an original image that has beendetermined by the determination unit as not having noise from theexterior superimposed on it. Because of this, a correction image withlittle noise can be created.

Furthermore, the correction image creation device of the presentinvention may be configured to acquire, as the original image, aradiographic image that has been captured by an imaging device, whichirradiates a subject with radiation from a radiation source and uses adetector to detect radiation that has passed through the subject tothereby capture a radiographic image of the subject, without irradiatinga subject with radiation from the radiation source. Because of this, acorrection image with little noise for offset correction with respect toa radiographic image can be easily created.

Furthermore, the correction image creation device of the presentinvention may be configured in such a way that the acquisition unitacquires, as the original image, an image that has been captured by asolid-state image sensor without the presence of incident light. Becauseof this, a correction image with little noise for offset correction withrespect to an image that has been captured by visible light imaging canbe easily created.

Furthermore, the correction image creation device of the presentinvention may be configured in such a way that the noise is at least oneof noise caused by scatter radiation, noise caused by an impact, andnoise caused by electromagnetic waves. Because of this, a correctionimage with little noise for offset correction can be easily created.

Furthermore, the correction image creation device of the presentinvention may be configured in such a way that the determination unitdetermines whether or not noise caused by scatter radiation issuperimposed by comparing, against a predetermined threshold value, meanvalues of pixel values in a plurality of regions in the original image.Because of this, noise caused by scatter radiation and superimposed on acorrection image for offset correction can be easily detected.

Furthermore, the correction image creation device of the presentinvention may be configured in such a way that the determination unitdetermines whether or not noise caused by an impact is superimposed onthe basis of numbers of pixels with respect to differences away from areference value of a histogram represented by differences in pixelvalues of corresponding pixels in an image for offset correction thathas already been created and an original image, differences in pixelvalues of corresponding pixels in original images, differences in pixelvalues of corresponding pixels in a difference image obtained from aplurality of original images on which noise is not superimposed and anoriginal image, or differences in pixel values of corresponding pixelsin a mean image of a plurality of original images on which noise is notsuperimposed and an original image, and numbers of pixels with respectto the differences. Because of this, noise caused by an impact andsuperimposed on a correction image for offset correction can be easilydetected.

Furthermore, the correction image creation device of the presentinvention may be configured in such a way that the determination unitdetermines whether or not noise caused by electromagnetic waves issuperimposed on the basis of the spread of a histogram represented bydifferences in pixel values of corresponding pixels in an image foroffset correction that has already been created and an original imageand numbers of pixels with respect to those differences. Because ofthis, noise caused by electromagnetic waves and superimposed on acorrection image for offset correction can be easily detected.

Furthermore, the correction image creation device of the presentinvention may be configured in such a way that the determination unituses, as the original image, an image obtained as a result of noisecaused by defective pixels having been removed by a median filter fromthe original image. Because of this, noise superimposed on a correctionimage for offset correction can be detected with good precision.

A radiographic imaging device of the present invention includes: thecorrection image creation device of the present invention; and animaging device that irradiates a subject with radiation from a radiationsource and uses a detector to detect radiation that has passed throughthe subject to thereby capture a radiographic image of the subject.

Consequently, according to the radiographic imaging device of thepresent invention, the radiographic imaging device acts in the same wayas the correction image creation device of the present invention, solike the correction image creation device of the present invention, whencreating a correction image for offset correction, a correction imagewith little noise can be easily created while ensuring that a correctionimage having noise superimposed thereon is not created.

An imaging device of the present invention includes: the correctionimage creation device of the present invention; and an imaging devicethat has a solid-state image sensor.

Consequently, according to the imaging device of the present invention,the imaging device acts in the same way as the correction image creationdevice of the present invention, so like the correction image creationdevice of the present invention, when creating a correction image foroffset correction, a correction image with little noise can be easilycreated while ensuring that a correction image having noise superimposedthereon is not created.

A program stored in a non-transitory computer readable medium of thepresent invention causes a computer to function as the correction imagecreation device of the present invention.

Consequently, according to the program of the present invention, theprogram acts in the same way as the offset image creation device of thepresent invention, so like the offset image creation device of thepresent invention, when creating a correction image for offsetcorrection, a correction image with little noise can be easily createdwhile ensuring that a correction image having noise superimposed thereonis not created.

An offset image creation method of the present invention includes:acquiring at least one original image, which is a basis when creating acorrection image used in offset correction with respect to an image thathas been obtained by imaging; determining whether or not noise from theexterior is superimposed on the original image; and cancelling creationof the correction image in a case in which it has been determined thatnoise from the exterior is superimposed on the original image.

According to the offset image creation method of the present invention,the offset image creation method acts in the same way as the offsetimage creation device of the present invention, so like the offset imagecreation device of the present invention, when creating a correctionimage for offset correction, a correction image with little noise can beeasily created while ensuring that a correction image having noisesuperimposed thereon is not created.

Advantageous Effects of Invention

According to the present invention, when creating a correction image foroffset correction, a correction image with little noise can be easilycreated while ensuring that a correction image having noise superimposedthereon is not created.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the overall configuration of a systemto which a radiographic imaging system pertaining to embodiments isapplied;

FIG. 2 is a drawing showing an example of the arrangement of devices, ina radiographic imaging room, of an imaging system pertaining to theembodiments;

FIG. 3 is a drawing showing the internal configuration of an electroniccassette pertaining to the embodiments;

FIG. 4 is a block diagram showing the configurations of relevant partsof an electrical system of the imaging system pertaining to theembodiments;

FIG. 5 is a flowchart showing a flow of imaging control processing inthe imaging system pertaining to the embodiments;

FIG. 6 is a drawing showing an example of an initial information inputscreen in the imaging system pertaining to the embodiments;

FIG. 7 is a flowchart showing a flow of offset image update processingin the imaging system pertaining to a first embodiment;

FIG. 8A is a schematic drawing showing an example of an image in whichthere is impact noise in the imaging system pertaining to the firstembodiment;

FIG. 8B is a schematic drawing showing an example of an image in whichthere is electromagnetic wave noise in the imaging system pertaining tothe first embodiment;

FIG. 9A and FIG. 9B are histograms showing pixel values of pixels in adifference image of an image captured the previous time and an imagecaptured this time in the imaging system pertaining to the embodiments,with the horizontal axes representing pixel values (QL values) and thevertical axes representing numbers of pixels, and FIG. 9A is a drawingshowing a case where there is no impact noise;

FIG. 9B is a drawing showing a case where there is impact noise;

FIG. 10 is a schematic drawing for describing impact noise detectionprocessing in the imaging system pertaining to the embodiments;

FIG. 11A is a histogram showing pixel values of pixels in a differenceimage of an image captured the previous time and an image captured thistime in the imaging system pertaining to the embodiments, with thehorizontal axis representing pixel values (QL values) and the verticalaxis representing numbers of pixels;

FIG. 11B is a drawing in which the scale of the graph in FIG. 11A hasbeen changed;

FIG. 12 is a schematic drawing for describing electromagnetic wave noisedetection processing in the imaging system pertaining to theembodiments;

FIG. 13 is a drawing showing an example of detection target regions inthe imaging system pertaining to the embodiments; and

FIG. 14 is a flowchart showing a flow of offset image update processingin the imaging system pertaining to a second embodiment.

DESCRIPTION OF EMBODIMENTS

Embodiments of the present invention will be described in detail belowwith reference to the drawings.

First Embodiment

FIG. 1 is a block diagram showing the overall configuration of a system10 to which a radiographic imaging system 18 pertaining to a firstembodiment is applied. First, the overall configuration of the system(hereinafter called a radiology information system, or “RIS”) 10 towhich the radiographic imaging system 18 pertaining to the firstembodiment is applied will be described with reference to FIG. 1.

The RIS 10 is a system for managing information such as medical serviceappointments and diagnostic records in a radiology department andconfigures part of a hospital information system (hereinafter called an“HIS”).

The RIS 10 has plural imaging request terminal devices (hereinaftercalled “terminal devices”) 12, an RIS server 14, and the radiographicimaging system (hereinafter called an “imaging system”) 18, which isinstalled in individual radiographic imaging rooms (or operating rooms)in a hospital, and these are connected to one another via an in-hospitalnetwork 16 comprising a wired or wireless local area network (LAN), forexample. The RIS 10 configures part of the HIS disposed in the samehospital, and an HIS server (not shown in the drawings) that manages theentire HIS is also connected to the in-hospital network 16.

The terminal devices 12 are devices for doctors and radiologictechnologists to input and browse diagnostic information and facilityreservations, and radiographic imaging requests and imaging reservationsare also made via the terminal devices 12. Each terminal device 12 isconfigured to include a display device and a personal computer, and theterminal devices 12 can communicate with one another via the RIS server14 and the in-hospital network 16.

The RIS server 14 receives the imaging requests from each of theterminal devices 12 and manages radiographic imaging schedules in theimaging systems 18, and the RIS server 14 is configured to include adatabase 14A.

The database 14A is configured to include: information relating topatients (subjects), such as attribute information (names, sexes, datesof birth, ages, blood types, body weights, and patient identifications(IDs), etc.), medical histories, consultation histories, radiographicimages captured in the past, etc.; information relating tolater-described electronic cassettes 32 used in the imaging systems 18,such as identification numbers (ID information), models, sizes,sensitivities, imaging sites for which the cassettes can be used(details of imaging requests that the cassettes can accommodate), datesof first use, numbers of times used, etc.; and environment informationrepresenting the environments in which the radiographic images arecaptured using electronic cassettes 32, that is, the environments inwhich the electronic cassettes 32 are used (e.g., radiographic imagingrooms, operating rooms, etc.).

The imaging systems 18 capture radiographic images as a result of beingoperated by a doctor or a radiologic technologist in response to aninstruction from the RIS server 14. Each imaging system 18 is equippedwith: a radiation generator 34 that irradiates a subject with a dose ofradiation X (see also FIG. 3) according to exposure conditions from aradiation source 130 (see also FIG. 2); an electronic cassette 32 thathas a built-in radiation detector 60 (see also FIG. 3) that absorbs theradiation X that has passed through the imaging target site of thesubject, generates charges, and produces image information representinga radiographic image on the basis of the generated charge quantity; acradle 40 that charges a battery built into the electronic cassette 32;and a console 42 that controls the electronic cassette 32, the radiationgenerator 34, and the cradle 40.

The console 42 acquires various types of information included in thedatabase 14A from the RIS server 14, stores the information in alater-described HDD 110 (see FIG. 4), and controls the electroniccassette 32, the radiation generator 34, and the cradle 40 on the basisof the information.

FIG. 2 is a drawing showing an example of the arrangement of thedevices, in a radiographic imaging room 44, of the imaging system 18pertaining to the first embodiment. As shown in FIG. 2, a rack 45 usedwhen performing radiographic imaging in an upright position and a bed 46used when performing radiographic imaging in a recumbent position areinstalled in the radiographic imaging room 44. The space in front of therack 45 serves as an imaging position 48 for a subject when performingradiographic imaging in the upright position, and the space above thebed 46 serves as an imaging position 50 for a subject when performingradiographic imaging in the recumbent position.

A holder 150 that holds the electronic cassette 32 is disposed on therack 45, and the electronic cassette 32 is held in the holder 150 whenperforming radiographic imaging in the upright position. Likewise, aholder 152 that holds the electronic cassette 32 is disposed in the bed46, and the electronic cassette 32 is held in the holder 152 whenperforming radiographic imaging in the recumbent position.

Furthermore, in order to enable both radiographic imaging in the uprightposition and radiographic imaging in the recumbent position usingradiation from the single radiation source 130, a supporting and movingmechanism 52 that supports the radiation source 130 in such a way thatthe radiation source 130 is rotatable about a horizontal axis (thedirection of arrow A in FIG. 2), is movable in the vertical direction(the direction of arrow B in FIG. 2), and is movable in the horizontaldirection (the direction of arrow C in FIG. 2) is disposed in theradiographic imaging room 44. Here, the supporting and moving mechanism52 is equipped with a drive source that rotates the radiation source 130about the horizontal axis, a drive source that moves the radiationsource 130 in the vertical direction, and a drive source that moves theradiation source 130 in the horizontal direction (none of the drivesources are shown in the drawings).

An accommodating portion 40A capable of storing the electronic cassette32 is formed in the cradle 40.

When the electronic cassette 32 is not in use, the battery built intothe electronic cassette 32 is charged by the cradle 40 in a state inwhich the electronic cassette 32 is stored in the accommodating portion40A of the cradle 40, and when radiographic imaging is to be performed,the electronic cassette 32 is removed from the cradle 40 by a radiologictechnologist, for example, and is held in the holder 150 of the rack 45if the imaging posture is the upright position or is held in the holder152 of the bed 46 if the imaging posture is the recumbent position.

Here, in the imaging system 18 pertaining to the present embodiment,various types of information are transmitted and received by wirelesscommunication between the radiation generator 34 and the console 42 andbetween the electronic cassette 32 and the console 42.

The electronic cassette 32 can be used not only in radiographic imagingrooms and operating rooms but also during medical examinations and onhospital rounds because it is portable.

FIG. 3 is a drawing showing the internal configuration of the electroniccassette 32 pertaining to the first embodiment. As shown in FIG. 3, theelectronic cassette 32 is equipped with a casing 54 comprising amaterial that allows the radiation X to pass through, and the electroniccassette 32 is given a waterproof and airtight structure. When theelectronic cassette 32 is used in an operating room, for example, thereis the concern that blood and/or various bacteria may adhere to theelectronic cassette 32. Therefore, by giving the electronic cassette 32a waterproof and airtight structure and sterilizing the electroniccassette 32 as needed, one electronic cassette 32 can be usedrepeatedly.

Inside the electronic cassette 54, a grid 58 that removes scatterradiation of the radiation X scattered by the subject, a radiationdetector 60 that detects the radiation X that has passed through thesubject, and a lead plate 62 that absorbs backscatter radiation of theradiation X are disposed in this order from an irradiated surface 56side of the casing 54 that is irradiated with the radiation X. Theirradiated surface 56 of the casing 54 may also be configured as thegrid 58.

A case 31 that accommodates electronic circuits including amicrocomputer and a rechargeable and removable battery 96A is disposedon one end side of the inside of the casing 54. The radiation detector60 and the electronic circuits run on power supplied from the battery96A disposed in the case 31. In order to avoid damage to the variouscircuits accommodated inside the case 31 in accompaniment withirradiation with the radiation X, it is preferred that a lead plate orthe like be disposed on the irradiated surface 56 side of the case 31.The electronic cassette 32 pertaining to the present embodiment is acuboid in which the shape of the irradiated surface 56 is rectangular,and the case 31 is disposed on one end portion in the long-dimensiondirection thereof.

Furthermore, a power switch 54A and an indicator 56A that indicateswhether the power switch 54A is switched on or off (power state),operating modes such as “ready” and “transmitting data”, and theoperating state of the electronic cassette 32 such as the capacityremaining in the battery 96A are disposed in predetermined positions onouter walls of the casing 54. In the electronic cassette 32 pertainingto the present embodiment, a light emitting diode is applied as theindicator 56A, but the indicator is not limited to this and may also beconfigured by other indicating means such as a light emitting elementother than a light emitting diode, a liquid crystal display, or anorganic EL display.

Moreover, a handle 54B that is gripped when moving the electroniccassette 32 is disposed in a predetermined position on an outer wall ofthe casing 54. In the electronic cassette 32 pertaining to the presentembodiment, the handle 54B is disposed in the center of a side walldisposed extending in the long-dimension direction of the irradiatedsurface 56 of the casing 54, but the place where the handle 54B isdisposed is not limited to this, and it goes without saying that thehandle 54B may also be disposed in another position, such as the centerof a side wall disposed extending in the short-dimension direction ofthe irradiated surface 56 or a position offset from the centers of theseside walls by a distance that takes into consideration lopsidedness inthe position of the center of gravity of the electronic cassette 32.

Next, the configurations of relevant parts of an electrical system ofthe imaging system 18 pertaining to the first embodiment will bedescribed with reference to FIG. 4. FIG. 4 is a block diagram showingthe configurations of relevant parts of the electrical system of theimaging system 18 pertaining to the first embodiment.

As shown in FIG. 4, the radiation detector 60 built into the electroniccassette 32 is configured as a result of photoelectric conversion layerthat absorbs the radiation X and converts the radiation X into chargesbeing layered on a TFT active matrix substrate 66. The photoelectricconversion layer comprises amorphous selenium (a-Se) whose maincomponent is selenium (e.g., having a content percentage of 50% ormore), and when the photoelectric conversion layer is irradiated withthe radiation X, it converts the radiation X with which it wasirradiated into charges by internally generating charges (electron-holepairs) of charge quantities corresponding to the dose of radiation withwhich it was irradiated. Instead of using a radiation-to-chargeconversion material like amorphous selenium that directly converts theradiation X into charges, the radiation detector 60 may also use aphosphor material and a photoelectric conversion element (photodiode) toindirectly convert the radiation X into charges. Gadolinium oxysulfate(GOS) and cesium iodide (CsI) are well known as phosphor materials. Inthis case, the phosphor material converts the radiation X into light,and the photodiode that is the photoelectric conversion element convertsthe light into charges. Furthermore, as the photoelectric conversionelement, an element using an organic photoelectric conversion materialmay be applied. Moreover, as the cesium iodide, CsI (TI), for example,may be applied.

Furthermore, numerous pixel portions 74 (in FIG. 4, the portions of thephotoelectric conversion layer corresponding to the individual pixelportions 74 are schematically shown as photoelectric conversion portions72) equipped with storage capacitors 68 that store the charges generatedin the photoelectric conversion layer and TFTs 70 for reading out thecharges stored in the storage capacitors 68 are arranged in a matrix onthe TFT active matrix substrate 66, and the charges generated in thephotoelectric conversion layer in accompaniment with the irradiation ofthe electronic cassette 32 with the radiation X are stored in thestorage capacitors 68 of the individual pixel portions 74. Because ofthis, image information carried in the radiation X with which theelectronic cassette 32 has been irradiated is converted into chargeinformation and held in the radiation detector 60.

Furthermore, plural gate lines 76, which are disposed extending in onedirection (a scan line direction; hereafter also called a “rowdirection”) and are for switching on and off the TFTs 70 of theindividual pixel portions 74, and plural data lines 78, which aredisposed extending in a direction (a signal line direction; hereinafteralso called a “column direction”) intersecting the gate lines 76 and arefor reading out the stored charges from the storage capacitors 68 viathe TFTs 70 that have been switched on, are disposed on the TFT activematrix substrate 66. The individual gate lines 76 are connected to agate line driver 80, and the individual data lines 78 are connected to asignal processing unit 82. When the charges are stored in the storagecapacitors 68 of the individual pixel portions 74, the TFTs 70 of theindividual pixel portions 74 are sequentially switched on by row bysignals supplied via the gate lines 76 from the gate line driver 80, andthe charges stored in the storage capacitors 68 of the pixel portions 74whose TFTs 70 have been switched on are transmitted through the datalines 78 as analog electrical signals and are input to the signalprocessing unit 82. Consequently, the charges stored in the storagecapacitors 68 of the individual pixel portions 74 are sequentially readout by row.

The electronic cassette 32 may be configured by a penetration sidesampling (PSS) where the photoelectric conversion layer and the TFTactive matrix substrate 66 are layered in this order from the sideirradiated with the radiation X, or may be configured by a irradiationside sampling (ISS) where the TFT active matrix substrate 66 and thephotoelectric conversion layer are layered in this order from the sideirradiated with the radiation X.

The signal processing unit 82 is equipped with amplifiers andsample-and-hold circuits that are disposed for each of the individualdata lines 78, and the charge signals transmitted through the individualdata lines 78 are amplified by the amplifiers and are thereafter held inthe sample-and-hold circuits. Furthermore, a multiplexer and ananalog-to-digital (A/D) converter are sequentially connected to theoutput sides of the sample-and-hold circuits, and the charge signalsheld in the individual sample-and-hold circuits are sequentially(serially) input to the multiplexer and are converted into digital imagedata by the A/D converter.

An image memory 90 is connected to the signal processing unit 82, andthe image data output from the A/D converter of the signal processingunit 82 are sequentially stored in the image memory 90. The image memory90 has a storage capacity capable of storing plural frames' worth ofimage data, and each time radiographic imaging is performed, the imagedata that have been obtained by the imaging are sequentially stored inthe image memory 90.

The image memory 90 is connected to a cassette control unit 92 thatcontrols the operation of the entire electronic cassette 32. Thecassette control unit 92 is configured to include a microcomputer and isequipped with a central processing unit (CPU) 92A, a memory 92B thatincludes a read-only memory (ROM) and a random access memory (RAM), anda nonvolatile storage unit 92C that comprises a hard disk drive (HDD) ora flash memory.

Moreover, a wireless communication unit 94 is connected to the cassettecontrol unit 92. The wireless communication unit 94 pertaining to thepresent embodiment is compatible with a wireless local area network(LAN) standard typified by IEEE (Institute of Electrical and ElectronicsEngineers) 802.11a/b/g, for example, and controls the transmission ofvarious types of information between the electronic cassette 32 andexternal devices by wireless communication. The cassette control unit 92can wirelessly communicate with the console 42, and can transmit andreceive various types of information to and from the console 42, via thewireless communication unit 94.

Furthermore, a power supply unit 96 is disposed in the electroniccassette 32, and the various circuits and elements described above (thegate line driver 80, the signal processing unit 82, the image memory 90,the wireless communication unit 94, the cassette control unit 92, etc.)run on power supplied from the power supply unit 96. The power supplyunit 96 has the aforementioned built-in battery (secondary battery) 96Aso as to not impair the portability of the electronic cassette 32, andthe power supply unit 96 supplies power to the various circuits andelements from the charged battery 96A. In FIG. 4, illustration of wiresconnecting the various circuits and elements to the power supply unit 96is omitted.

The console 42 is configured as a server computer and is equipped with adisplay 100, which displays operation menus and captured radiographicimages, and an operation panel 102, which is configured to includeplural keys and to which various types of information and operationinstructions are input.

Furthermore, the console 42 pertaining to the present embodiment isequipped with a CPU 104 that controls the operation of the entiredevice, a ROM 106 in which various programs including a control programare stored beforehand, a RAM 108 that temporarily stores various typesof data, a HDD 110 that stores and holds various types of data, adisplay driver 112 that controls the display of various types ofinformation on the display 100, and an operation input detection unit114 that detects states of operation with respect to the operation panel102. Furthermore, the console 42 is equipped with a wirelesscommunication unit 118 that transmits and receives various types ofinformation such as later-described exposure conditions to and from theradiation generator 34 by wireless communication and also transmits andreceives various types of information such as image data to and from theelectronic cassette 32 by wireless communication.

The CPU 104, the ROM 106, the RAM 108, the HDD 110, the display driver112, the operation input detection unit 114, and the wirelesscommunication unit 118 are connected to one another via a system busBUS. Consequently, the CPU 104 can access the ROM 106, the RAM 108, andthe HDD 110, can control the display of various types of information onthe display 110 via the display driver 112, and can control thetransmission and reception of various types of information to and fromthe radiation generator 34 and the electronic cassette 32 via thewireless communication unit 118. Furthermore, the CPU 104 can graspstates of operation by a user with respect to the operation panel 102via the operation input detection unit 114.

The radiation generator 34 is equipped with the radiation source 130, awireless communication unit 132 that transmits and receives varioustypes of information such as the exposure conditions to and from theconsole 42, and a radiation source control unit 134 that controls theradiation source 130 on the basis of the received exposure conditions.

The radiation source control unit 134 is also configured to include amicrocomputer and stores the received exposure conditions and so forth.The exposure conditions received from the console 42 include informationsuch as tube voltage, tube current, and exposure duration. The radiationsource control unit 134 causes the radiation X to be emitted from theradiation source 130 on the basis of the received exposure conditions.

Next, a flow of imaging control processing in the imaging system 18pertaining to the first embodiment will be described.

FIG. 5 is a flowchart showing a flow of the imaging control processingin the imaging system 18 pertaining to the first embodiment. The imagingcontrol processing is executed by the CPU 104 of the console 42 whenperforming radiographic imaging, and a program for performing theimaging control processing is stored beforehand in a predeterminedregion of the ROM 106.

In step S201, the CPU 104 controls the display driver 112 to cause thedisplay 100 to display a predetermined initial information input screen.

FIG. 6 is a drawing showing an example of the initial information inputscreen in the imaging system 18 pertaining to the first embodiment. Asshown in FIG. 6, displayed on the initial information input screen are amessage prompting the radiographer to input information relating tovarious items, such as the name of the subject on which radiographicimaging is about to be performed, the imaging site, the posture duringimaging (in the present embodiment, the recumbent position or theupright position), and the exposure conditions for exposure to theradiation X during imaging (in the present embodiment, the tube voltage,the tube current, and the exposure duration when exposing the subject tothe radiation X), input fields for inputting these pieces of initialinformation, and a “finished” button indicating that the radiographerhas finished inputting the information. The radiographer selects the“finished” button after inputting the initial information relating tothe various items via the operation panel 102 in accordance with theinitial information input screen.

In step S203, the CPU 104 determines whether or not the input of theinitial information has been completed. At this time, the CPU 104determines that the input of the initial information has been completedin a case where, for example, the “finished” button on the initialinformation input screen has been selected.

In a case where it has been determined in step S203 that the input ofthe initial information has been completed, in step S205 the CPU 104estimates, on the basis of the initial information that has been input,the point in time at which exposure to the radiation X will end(hereinafter called “the point in time at which exposure will end”)whose reference is the point in time at which charge storage is startedby the radiation detector 60.

In the imaging system 18 pertaining to the present embodiment, the CPU104 estimates the point in time at which exposure will end by adding theexposure duration that was input in the initial information input screento a time period from when charge storage by the radiation detector 60is started to until exposure to the radiation X is actually started,which is determined beforehand by the point in time at which chargestorage by the radiation detector 60 is started in accordance with theprocessing of later-described step 211 in the electronic cassette 32 anda time period from the point in time at which the start of exposure tothe radiation X has been instructed by the processing of later-describedstep 213 in the radiation generator 34 to until exposure is actuallystarted.

Next, in step S207, the CPU 104 executes offset image update processingthat produces image data (hereinafter called “offset image data”) forcorrecting image data (hereinafter called “subject image data”) thathave been obtained by radiographic imaging by the radiation detector 60,by causing imaging by the radiation detector 60 to be executed in thesame charge storage time period as the applied charge storage timeperiod without causing radiation to be generated from the radiationgenerator 34.

FIG. 7 is a flowchart showing a flow of the offset image updateprocessing in the imaging system 18 pertaining to the first embodiment.The offset image update processing is executed by the CPU 104 of theconsole 42, and a program for performing the offset image updateprocessing is stored beforehand in a predetermined region of the ROM106.

In step S301, the CPU 104 transmits, to the electronic cassette 32 viathe wireless communication unit 118, and together with informationrepresenting the applied charge storage time period and informationrepresenting the number of times imaging is to be performed (in thepresent embodiment, four times), instruction information instructing theelectronic cassette 32 to execute imaging implementation processing inorder to acquire an original image, which is a basis when creating acorrection image used in offset correction. In response to this, theelectronic cassette 32 performs a reset operation that discharges thecharges being stored in the radiation detector 60 at this point in time,thereafter performs, a number of times equal to the designated number oftimes, imaging by the radiation detector 60 in the received appliedcharge storage time period, and transmits the image data that have beenobtained thereby to the console 42 via the wireless communication unit94.

Therefore, in step S303, the CPU 104 determines whether or not it hasreceived the image data via the wireless communication unit 118 from theelectronic cassette 32. At this time, the CPU 104 determines that it hasreceived the image data in a case where it has received image datarepresenting plural images that have been obtained by performing imaginga number of times equal to the designated number of times.

In a case where it has been determined in step S303 that the CPU 104 hasreceived the image data, the CPU 104 determines, in regard to each ofthe images represented by the received image data, whether or not thereare various types of noise in those images (images for creating an imagefor offset correction). In the first embodiment, the CPU 104 determineswhether or not there is impact noise, electromagnetic wave noise, andscatter radiation noise in regard to each of the images.

Impact noise is noise that occurs when the portable electronic cassette32 falls or collides with an object such as an obstacle and vibration isimparted to the electronic cassette 32. Electromagnetic wave noise isnoise that occurs because of electromagnetic waves generated fromanother device such as a personal computer (PC) disposed in theneighborhood of the electronic cassette 32. Furthermore, scatterradiation noise is noise which, in a case where in addition to theradiation generator 34 another radiation generator that generatesradiation such as X-rays is disposed in the neighborhood of theelectronic cassette 32, occurs as a result of scatter radiation from theradiation generated by that other radiation generator being madeincident on the electronic cassette 32.

FIG. 8A is a schematic drawing showing an example of an image in whichthere is impact noise in the imaging system 18 pertaining to the firstembodiment, and FIG. 8B is a schematic drawing showing an example of animage in which there is electromagnetic wave noise in the imaging system18 pertaining to the first embodiment. As shown in FIG. 8A, in a casewhere there is impact noise in an image 160 that has been captured bythe electronic cassette 32, for example, linear noise N temporarilyoccurs in part of the image 160 (a region corresponding to lines fromwhich signals were read by the signal processing unit 82 at the momentwhen the impact occurred in the electronic cassette 32). Furthermore, asshown in FIG. 8B, in a case where there is electromagnetic wave noise inan image 160 that has been captured by the electronic cassette 32,linear noise N temporarily occurs in the entire image 160.

First, in step S305, the CPU 104 determines whether or not impact noisehas been detected from the received image data.

FIGS. 9A and 9B are histograms showing pixel values of pixels in adifference image of an image captured the previous time and an imagecaptured this time in the imaging system 18 pertaining to the firstembodiment, with the horizontal axes representing pixel values (QLvalues) and the vertical axes representing numbers of pixels; FIG. 9A isa drawing showing a case where there is no impact noise and FIG. 9B is adrawing showing a case where there is impact noise. The QL values arevalues corresponding to the density of the film of the radiographicimage obtained by applying radiation, and the QL values may be thevalues of gradation signals themselves or may be signals obtained byperforming predetermined processing on the gradation signals.Furthermore, the pixel values are padded in the entire image by adding4000 QL, for example, to the pixel value of each pixel in the differenceimage.

As shown in FIG. 9A, in a case where there is no impact noise in theimages captured by the electronic cassette 32, the histogram of thepixel values in the difference image (that is, the differences in thepixel values of corresponding pixels in the image captured the previoustime and the image captured this time) shows a regular distribution. Onthe other hand, as shown in FIG. 9B, in a case where there is impactnoise in the images captured by the electronic cassette 32, noisecorresponding to the impact noise shown in FIG. 8A occurs at the foot ofthe peak in the histogram. This is because in a case where there isimpact noise in either the image captured the previous time or the imagecaptured this time, the pixel values of the pixels in the differenceimage become larger in the pixel region corresponding to the sectionwhere the impact noise is.

FIG. 10 is a schematic drawing for describing impact noise detectionprocessing in the imaging system 18 pertaining to the first embodiment.As shown in FIG. 10, the CPU 104 produces a difference image of thefirst and second images among the plural images (in the presentembodiment, four). The pixel value of each pixel in the difference imageis padded by adding 4000 QL, for example, to it. Then, the CPU 104performs mean reduction processing on the produced difference image. Themean reduction processing is processing that uses a pixel region of apredetermined size (in the present embodiment, a rectangular pixelregion comprising two in a primary direction x two in a secondarydirection) as a single pixel that takes as its pixel value the meanvalue of the pixel values of that pixel region. In a case where the meanreduction processing is unnecessary, the mean reduction processing maybe omitted.

Furthermore, the CPU 104 performs median filter processing on thereduced image on which the mean reduction processing has been performed(the difference image in the case where the mean reduction processing isnot performed). The median filter processing is processing which, whenthe pixel values of each pixel in a pixel region of a predetermined size(in the present embodiment, a rectangular pixel region comprising fivein a main direction×five in a secondary direction) have been arranged inascending order, uses the pixel value positioned in the center as thepixel value of the pixel in the center of that pixel region. With thismedian filter processing, point-like noise caused by pixel defects, forexample, can be removed from the mean reduction image.

Moreover, the CPU 104 determines, per pixel, whether or not thedifference between the pixel value and a reference value (a QL value of4000) is equal to or greater than a predetermined first threshold valuein regard to the median image on which the median filter processing hasbeen performed and counts the total number of pixels that are equal toor greater than the first threshold value. The first threshold value isset to an upper limit value that can be regarded as random noise in thehistograms shown in FIG. 8. Furthermore, pixels whose pixel values areequal to or greater than the first threshold value are pixels in whichthe absolute values of the differences in the pixel values ofcorresponding pixels in the first image and the second image are largeand in which there is the potential for there to be impact noise.

The CPU 104 determines that there is impact noise in the first or secondimage in a case where the total number of pixels that are equal to orgreater than the first threshold value is equal to or greater than apredetermined second threshold value. The second threshold value is setto a numerical value representing an upper limit value with which thetotal number of pixels that are equal to or greater than the firstthreshold value can be regarded as random noise. Furthermore, in a casewhere it is known that there is no impact noise in the first image, itcan be determined that there is impact noise in the second image.

In a case where impact noise has not been detected in the first andsecond images as a result of performing the impact noise detectionprocessing in regard to the first and second images, the CPU 104performs the impact noise detection processing in regard to thedifference image of the first and second images and the third image. Andin a case where impact noise has likewise not been detected in the thirdimage, the CPU 104 performs the impact noise detection processing inregard to a difference image of that difference image and the thirdimage and the fourth image. At this time, in a case where impact noisehas been detected in any of the first to fourth images at any stage, theCPU 104 determines that impact noise has been detected and cancels theimpact noise detection processing. In this way, by producing adifference image of other plural images in which impact noise has notbeen detected and producing a difference image of this difference imageand an image taken as a detection target, error caused by random noisecan be reduced.

In the first embodiment, the CPU 104 uses a difference image in theimpact noise detection processing, but the CPU 104 is not limited tothis and may also use a mean image instead of a difference image in theimpact noise detection processing. That is, the CPU 104 may also beconfigured to perform the impact noise detection processing in regard tothe first and second images, perform the impact noise detectionprocessing in regard to a mean image of the first and second images andthe third image, and perform the impact noise detection processing inregard to a mean image of the first to third images and the fourthimage.

Furthermore, in the first embodiment, in the impact noise detectionprocessing, the CPU 104 uses the first and second images as detectiontarget images and produces a difference image of the first and secondimages, but the CPU 104 is not limited to this and may also produce adifference image or a mean image of an image already stored in the RAM108 as an image for offset correction and each of the first to fourthimages.

In a case where it has been determined in step S305 that impact noisehas not been detected, in step S307 the CPU 104 determines whether ornot electromagnetic wave noise has been detected from the received imagedata.

FIG. 11A is a histogram showing pixel values of pixels in a differenceimage of an image captured the previous time and an image captured thistime in the imaging system 18 pertaining to the first embodiment, withthe horizontal axis representing pixel values (QL values) and thevertical axis representing numbers of pixels, and FIG. 11B is a drawingin which the scale of the graph in FIG. 11A has been changed. The pixelvalues are padded in the entire image by adding 4000 QL, for example, tothe pixel value of each pixel in the difference image.

As shown in FIGS. 11A and 11B, in a case where there is noelectromagnetic wave noise in the images that have been captured by theelectronic cassette 32, the histogram of the differences in the pixelvalues shows a regular distribution having a sharp peak. On the otherhand, in a case where there is electromagnetic wave noise in the imagesthat have been captured by the electronic cassette 32, the spread of thepeak in the histogram differs from the case where there is noelectromagnetic wave noise in that the width of the peak becomes widerand the height of the peak becomes lower because, as mentioned above,electromagnetic wave noise is noise that occurs in the entire image.This is because in a case where there is no electromagnetic wave noisein the image captured the previous time but there is electromagneticwave noise in the image captured this time, the differences in the pixelvalues of the corresponding pixels in the image captured the previoustime and the image captured this time become larger in the entire image,that is, the pixel values of the pixels in the difference image becomelarger.

FIG. 12 is a schematic drawing for describing electromagnetic wave noisedetection processing in the imaging system 18 pertaining to the firstembodiment. As shown in FIG. 12, the CPU 104 produces a difference imageof an image for offset correction the previous time (an image alreadystored in the RAM 108 as an image for offset correction) and the firstimage. The pixel value of each pixel in the difference image is paddedby adding 4000 QL, for example, to it. Furthermore, the aforementionedmean reduction processing and median filter processing are performed onthe first to fourth images.

Furthermore, the CPU 104 produces, in regard to the produced differenceimage, a histogram in which the horizontal axis represents differencesin pixel values (QL values) and the vertical axis represents numbers ofpixels, and derives the spread of the width of the peak in thehistogram. Then, the CPU 104 determines whether or not the width of thepeak is equal to or greater than a predetermined third threshold value.The third threshold value is set to a numerical value representing anupper limit value with which the width of the peak can be regarded asrandom noise. In consideration of the fact that the width of the peak inthe histogram becomes wider in a case where there is electromagneticwave noise in the image captured this time, the CPU 104 determines thatthere is electromagnetic wave noise in the image captured this time in acase where the width of the peak is equal to or greater than the thirdthreshold value.

The CPU 104 performs the electromagnetic wave noise detection processingin regard to the first to fourth images and determines thatelectromagnetic wave noise has been detected in a case whereelectromagnetic wave noise has been detected in any of the images.

In a case where there is not an image already stored in the RAM 108 asan image for offset correction, in the electromagnetic wave noisedetection processing, the CPU 104 produces a difference image withrespect to each of the first to fourth images. In a case where there iselectromagnetic wave noise in any of the first to fourth images, byutilizing the fact that the spread of the histogram differs in thatimage with respect to another image, it can be determined that there iselectromagnetic wave noise in the image in which the spread differs withrespect to another image.

Furthermore, in the first embodiment, the CPU 104 determines whether ornot there is electromagnetic wave noise by determining whether or notthe width of the peak in the histogram is equal to or greater than thethird threshold value, but the determination method is not limited tothis, and the CPU 104 can also make the determination by any ofdetermining whether or not the half width of the peak is equal to orgreater than a predetermined value, determining whether or not theheight of the peak is equal to or less than a predetermined value, anddetermining whether or not the ratio of the height of the peak withrespect to the half width of the peak is equal to or greater than apredetermined value.

In a case where it has been determined in step S307 that electromagneticwave noise has not been detected, in step S309 the CPU 104 determineswhether or not scatter radiation noise has been detected from thereceived image data. Here, utilizing the fact that, in a case wherescatter radiation of X-rays or the like has been made incident on theelectronic cassette 32, the pixel density in the pixel region where thescatter radiation was made incident differs greatly from the pixeldensity in pixel regions where the scatter radiation was not madeincident, the CPU 104 determines whether or not there is scatterradiation noise by detecting whether or not there is a region in whichthe pixel density greatly differs. The aforementioned mean reductionprocessing and median filter processing are performed on the first tofourth images.

FIG. 13 is a drawing showing an example of detection target regions 160a in the imaging system 18 pertaining to the first embodiment. As shownin FIG. 13, in each of the first to fourth images 160, plural (in thepresent embodiment, nine) pixel regions of a predetermined size locatedin predetermined regions are preset as the detection target regions 160a.

The CPU 104 derives the mean value of the pixel values of the pixels ineach of the plural target detection regions 160 a in regard to each ofthe first to fourth images 160 and determines whether or not the derivedmean values are equal to or greater than a predetermined fourththreshold value. The fourth threshold value is the numerical value of anupper limit value with which the mean values of the pixel values of thepixels of the target detection regions 160 a can be regarded as randomnoise. Furthermore, the CPU 104 determines that there is scatterradiation noise in the image being taken as the determination target ina case where the mean value of the pixel values in any of the detectiontarget regions 160 a is equal to or greater than the fourth thresholdvalue.

The CPU 104 determines that scatter radiation noise has been detected ina case where scatter radiation noise has been detected in any of thefirst to fourth images.

In a case where it has been determined in step S309 that scatterradiation noise has not been detected, in step S311 the CPU 104 producesa mean image of the first to fourth images as an image for offsetcorrection and stores the produced image for offset in a predeterminedregion of the RAM 108 to thereby update the image for offset correction.

Furthermore, in a case where it has been determined in step S305 thatimpact noise has not been detected, or in a case where it has beendetermined in step S307 that electromagnetic wave noise has not beendetected, or in a case where it has been determined in step S309 thatscatter radiation noise has not been detected, in step S313 the CPU 104stands by until a predetermined amount of time (in the presentembodiment, 10 minutes) elapses without producing an image for offsetcorrection based on the image data received in step S303, and thereafterthe CPU 104 returns to step S301 and again performs the processing ofsteps S301 to S313. The predetermined amount of time is an amount oftime needed until the occurrence of the various types of noise describedabove settles.

When the radiographer selects the “finished” button on the initialinformation input screen in step S203, depending on the posture(recumbent position or upright position) of the subject that was inputon the initial information input screen, the radiographer either putsthe electronic cassette 32 into the holder 152 disposed in the bed 46and positions the subject in the recumbent position in the imagingposition 50 in the space above the bed 46 or puts the electroniccassette 32 into the holder 150 in the rack 45 and has the subject standin the imaging position 48 in the space in front of the rack 45. Next,the radiographer operates the supporting and moving mechanism 52 todispose the radiation source 130 of the radiation generator 34 in frontof the imaging position.

In step S209, the CPU 104 transmits, to the radiation generator 34 viathe wireless communication unit 118, the exposure conditions that wereinput on the initial information input screen to thereby set theexposure conditions. In response to this, the radiation source controlunit 134 prepares for exposure in the received exposure conditions.

In step S211, the CPU 104 transmits, to the electronic cassette 32 viathe wireless communication unit 118, instruction information instructingthe electronic cassette 32 to start executing imaging implementationprocessing that implements radiographic imaging. In response to this,the electronic cassette 32 starts executing later-described imagingimplementation processing.

In step S213, the CPU 104 transmits, to the radiation generator 34 viathe wireless communication unit 118, instruction information instructingthe radiation generator 34 to start the exposure. In response to this,the radiation generator 34 generates and emits the radiation X from theradiation source 130 at the tube voltage, tube current, and exposureduration corresponding to the exposure conditions received from theconsole 42 in accordance with the processing of step S209. In responseto this, the electronic cassette 32 performs radiographic imaging by theimaging implementation processing and transmits the subject image dataobtained thereby to the console 42 via the wireless communication unit94.

Therefore, in step S215, the CPU 104 determines whether or not it hasreceived the subject image data from the electronic cassette 32. In acase where it has been determined in step S215 that the CPU 104 hasreceived the subject image data, in step S217 the CPU 104 transmits, tothe electronic cassette 32 via the wireless communication unit 118,instruction information instructing the electronic cassette 32 to stopthe power supply that was started in step S205. In response to this, theelectronic cassette 32 controls the power supply unit 96 to stop thepower supply.

In step S219, the CPU 104 executes, with respect to the received subjectimage data, image processing that performs offset correction bysubtracting, per pixel, the image data of the image for offsetcorrection that was updated in S207 and which thereafter performsvarious types of correction such as switching element and leak currentcorrection and amp offset voltage correction.

In step S221, the CPU 104 stores in the HDD 110 the subject image dataon which the image processing has been performed (hereinafter called“corrected image data”). Furthermore, in step S223, the CPU 104 controlsthe display driver 112 in such a way as to cause the radiographic imagerepresented by the corrected image data to be displayed by the display100 for checking and so forth. Moreover, in step S225, the CPU 104transmits the corrected image data to the RIS server 14 via thein-hospital network 16 and thereafter ends the radiographic imagingprocessing program. The corrected image data that have been transmittedto the RIS server 14 are stored in the database 14A and can be used by adoctor to read the captured radiographic image and make a diagnosis.

As described in detail above, according to the first embodiment, the CPU104 acquires at least one original image, which is a basis when creatinga correction image used in offset correction with respect to an imagethat has been obtained by imaging, determines whether or not noise fromthe exterior is superimposed on the original image, and, in a case whereit has been determined that noise from the exterior is superimposed onthe original image, cancels production of the correction image using theoriginal image on which the noise is superimposed. Because of this, whencreating a correction image for offset correction, a correction imagewith little noise can be easily created while ensuring that a correctionimage having noise superimposed thereon is not created.

It is not invariably necessary for the processing of steps S305, S307,and S309 to be performed in the aforementioned order, and the processingmay also be executed in an arbitrarily switched order. Furthermore, itis not invariably necessary for the processing of steps S305, S307, andS309 to all be executed, and the CPU 104 may also be configured toselectively execute the processing of steps S305, S307, and S309 inaccordance with device characteristics and environmental conditions.

Furthermore, when an imaging instruction made by a radiographer has beeninput while the CPU 104 is performing the offset image updateprocessing, the CPU 104 may also be configured in such a way that theimaging is started after the CPU 104 completes the processing of stepsS301 to S313 or in such a way that the CPU 104 cancels the offset imageupdate processing without updating the image for offset correction anduses an image for offset correction that is already stored. In a casewhere there is an image being captured when an imaging instruction madeby a radiographer has been input while the CPU 104 is performing theoffset image update processing, the CPU 104 cancels the offset imageupdate processing at the stage when the capture of that image isfinished.

Furthermore, in the offset image update processing, the imaging system18 pertaining to the first embodiment creates an image for offset usingplural images that have been obtained by performed imaging plural times,but the imaging system 18 is not limited to this and may also create animage for offset using one image that has been obtained by performingimaging one time. In this case, when the CPU 104 performs the impactnoise detection processing in step S305, the CPU 104 uses the image foroffset correction that is already stored in the RAM 108 and the oneimage that has been obtained by imaging.

Furthermore, the imaging system 18 pertaining to the first embodimentperforms the offset image update processing just before performingimaging with the electronic cassette 32, but the timing when the offsetimage update processing is performed is not limited to this, and theoffset image update processing can be performed at an arbitrary timing.

Furthermore, the imaging system 18 pertaining to the first embodimentperforms the offset image update processing with respect to theelectronic cassette 32 that captures radiographic images, but theimaging system 18 is not limited to this and may also perform the offsetimage update processing with respect to an imaging device that performsimaging with a solid-state image sensor. In this case, the CPU 104acquires, as the original image, an image that has been captured by thesolid-state image sensor without the presence of incident light.

Second Embodiment

A radiographic imaging system 10 pertaining to a second embodiment willbe described in detail below using the attached drawings. Like theimaging system 10 pertaining to the first embodiment, the radiographicimaging system 10 pertaining to the second embodiment has theconfigurations shown in FIG. 1 to FIG. 4. The same reference signs willbe assigned to configurations that are the same as those in the firstembodiment, and redundant description will be omitted.

When the imaging system 18 of the first embodiment updates the image foroffset correction, in a case where there is noise in any of the fourimages, it does not update the image for offset correction using thosefour images. In contrast, in a case where there is noise in any of thefour images, the imaging system 18 pertaining to the second embodimentuses only the images not affected by noise to produce and update theimage for offset correction.

A flow of imaging control processing in the imaging system 18 pertainingto the second embodiment will be described.

First, the CPU 104 performs the processing of step S201 to S205 in thesame way as in the first embodiment. Then, in step S207, the CPU 104performs offset image update processing.

FIG. 14 is a flowchart showing a flow of the offset image updateprocessing in the imaging system 18 pertaining to the presentembodiment. The offset image update processing is executed by the CPU104 of the console 42, and a program for performing the offset imageupdate processing is stored beforehand in a predetermined region of theROM 106.

In steps S401 to S403, the CPU 104 performs the same processing as insteps S301 to S303. In step S404, the CPU 104 selects, from the imagesrepresented by the image data received in step S403, an image to serveas a detection target of the various types of noise described above. Insteps S405 to S409, the CPU 104 performs the same processing as in stepsS305 to S309 in regard to the image selected as the detection target instep 404. Then, in a case where it has been determined in step S409 thatscatter radiation noise has not been detected, in step S411 the CPU 104regards the image serving as the detection target in steps S405 to S409as an image to be used in the production of an image for offsetcorrection.

When performing the impact noise detection processing in step S405, theCPU 104 uses an image for offset correction that is already stored inthe RAM 108 and one image that has been obtained by imaging.

In a case where it has been determined in step S405 that impact noisehas been detected, or in a case where it has been determined in stepS407 that electromagnetic wave noise has been detected, or in a casewhere it has been determined in step S409 that scatter radiation noisehas been detected, in step S413 the CPU 104 regards the image serving asthe detection target in steps S405 to S409 as an image not to be used inthe production of an image for offset correction.

In step S415, the CPU 104 determines whether or not there areunprocessed image data, that is, images on which the processing of stepsS405 to S413 has not been performed. In a case where it has beendetermined in step S415 that there are unprocessed image data, the CPU104 returns to step S405 and performs the processing of steps S405 toS413 in regard to the image represented by the unprocessed image data.

In a case where it has been determined in step S415 that there are nounprocessed image data, in step S417 the CPU 104 determines whether ornot there is an image to be used in the production of an image foroffset correction, that is, an image that was in step S411 regarded asan image to be used in the production of an image for offset correction.

In a case where it has been determined in step S415 that there is animage to be used in the production of an image for offset correction, instep S419 the CPU 104 updates the image for offset correction bystoring, in a predetermined region of the RAM 108 as an image for offsetcorrection, a mean image of the images that were in step S411 regardedas images to be used in the production of an image for offsetcorrection. On the other hand, in a case where it has been determined instep S415 that there is not an image to be used in the production of animage for offset correction, the CPU 104 does not update the image foroffset correction.

Then, the CPU 104 performs the processing of steps S209 to S225 in thesame way as in the first embodiment and ends the imaging controlprocessing program.

As described in detail above, according to the second embodiment, theCPU 104 creates a correction image using an original image that has beendetermined as not having noise from the exterior superimposed on it.Because of this, when creating a correction image for offset correction,a correction image with little noise can be easily created whileensuring that a correction image having noise superimposed thereon isnot created.

In each of the above embodiments, a case was described where X-rays wereapplied as the radiation of the present invention, but the presentinvention is not limited to this and also includes other forms ofradiation, such as alpha radiation and gamma radiation, for example.

The present invention has been described above using embodiments, butthe technical scope of the present invention is not limited to the scopedescribed in the embodiments. Various changes and improvements can bemade to the embodiments without departing from the gist of theinvention, and embodiments to which such changes or improvements havebeen made are included in the technical scope of the present invention.

What is claimed is:
 1. A correction image creation device comprising: anacquisition unit that acquires at least one original image, which is abasis when creating a correction image used in offset correction withrespect to an image that has been obtained by imaging; a determinationunit that determines whether or not noise, from an exterior, issuperimposed on the original image; and a cancellation unit that cancelscreation of the correction image in a case in which it has beendetermined by the determination unit that noise from the exterior issuperimposed on the original image.
 2. The correction image creationdevice according to claim 1, wherein, in a case in which it has beendetermined that noise from the exterior is superimposed on the originalimage, the cancellation unit cancels creation of the correction imagethat uses the original image on which the noise has been superimposed.3. The correction image creation device according to claim 2, furthercomprising a creation unit that creates the correction image, using anoriginal image that has been determined by the determination unit as nothaving noise from the exterior superimposed on it.
 4. The correctionimage creation device according to claim 1, wherein the correction imagecreation device acquires, as the original image, a radiographic imagethat has been captured by an imaging device, which irradiates a subjectwith radiation from a radiation source and uses a detector to detectradiation that has passed through the subject to thereby capture aradiographic image of the subject, without irradiating a subject withradiation from the radiation source.
 5. The correction image creationdevice according to claim 1, wherein the acquisition unit acquires, asthe original image, an image that has been captured by a solid-stateimage sensor without the presence of incident light.
 6. The correctionimage creation device according to claim 1, wherein the noise is atleast one of noise caused by scatter radiation, noise caused by animpact or noise caused by electromagnetic waves.
 7. The correction imagecreation device according to claim 1, wherein the determination unitdetermines whether or not noise caused by scatter radiation issuperimposed, by comparing, against a predetermined threshold value,mean values of pixel values in a plurality of regions in the originalimage.
 8. The correction image creation device according to claim 1,wherein the determination unit determines whether or not noise caused byan impact is superimposed, on the basis of numbers of pixels withrespect to differences away from a reference value of a histogramrepresented by differences in pixel values of corresponding pixels in animage for offset correction that has already been created and anoriginal image, differences in pixel values of corresponding pixels inoriginal images, differences in pixel values of corresponding pixels ina difference image obtained from a plurality of original images on whichnoise is not superimposed and an original image, or differences in pixelvalues of corresponding pixels in a mean image of a plurality oforiginal images on which noise is not superimposed and an originalimage, and numbers of pixels with respect to the differences.
 9. Thecorrection image creation device according to claim 1, wherein thedetermination unit determines whether or not noise caused byelectromagnetic waves is superimposed, on the basis of the spread of ahistogram represented by differences in pixel values of correspondingpixels in an image for offset correction that has already been createdand an original image and numbers of pixels with respect to thosedifferences.
 10. The correction image creation device according to claim1, wherein the determination unit uses, as the original image, an imageobtained as a result of noise caused by defective pixels having beenremoved by a median filter from the original image.
 11. A radiographicimaging device comprising: an imaging device that irradiates a subjectwith radiation from a radiation source and uses a detector to detectradiation that has passed through the subject to thereby capture aradiographic image of the subject, and a correction image creationdevice comprising: an acquisition unit that acquires at least oneoriginal image, which is a basis when creating a correction image usedin offset correction with respect to an image that has been obtained byimaging; a determination unit that determines whether or not noise, froman exterior, is superimposed on the original image; and a cancellationunit that cancels creation of the correction image in a case in which ithas been determined by the determination unit that noise from theexterior is superimposed on the original image, wherein the correctionimage creation device acquires, as the original image, a radiographicimage that has been captured by the imaging device without irradiating asubject with radiation from the radiation source.
 12. The radiographicimaging device according to claim 11, wherein, in a case in which it hasbeen determined that noise from the exterior is superimposed on theoriginal image, the cancellation unit cancels creation of the correctionimage that uses the original image on which the noise has beensuperimposed.
 13. The radiographic imaging device according to claim 12,further comprising a creation unit that creates the correction image,using an original image that has been determined by the determinationunit as not having noise from the exterior superimposed on it.
 14. Animaging device comprising: the correction image creation deviceaccording to claim 5; and an imaging device that has a solid-state imagesensor.
 15. A non-transitory computer readable medium storing a programfor causing a computer to function as the correction image creationdevice according to claim
 1. 16. The non-transitory computer readablemedium according to claim 15, wherein, in a case in which it has beendetermined that noise from the exterior is superimposed on the originalimage, the cancellation unit cancels creation of the correction imagethat uses the original image on which the noise has been superimposed.17. The non-transitory computer readable medium according to claim 16,further comprising a creation unit that creates the correction image,using an original image that has been determined by the determinationunit as not having noise from the exterior superimposed on it.
 18. Acorrection image creation method comprising: acquiring at least oneoriginal image, which is a basis when creating a correction image usedin offset correction with respect to an image that has been obtained byimaging; determining whether or not noise, from an exterior, issuperimposed on the original image; and cancelling creation of thecorrection image in a case in which it has been determined that noisefrom the exterior is superimposed on the original image.